For All Optical networks, the wavelength and/or subband (group of wavelengths) assignment for traffic from the source node to the destination node can involve blocking at intermediate nodes, especially when the number of nodes and the number of different demands for bandwidth from point to point in a network is very large. An example of blocking in an optical network 10 is described with reference to FIG. 1. Therein, a first demand 12 includes an optical signal route from origin node 14 through optical switching nodes 16 and 18 to destination node 20. Also, a second demand 22 includes an optical signal route from origin node 24 through optical switching nodes 16, 18, and 20, to destination node 28. Further, a third demand 30 includes an optical signal route from origin node 32 through optical switching node 18, to destination node 20. Blocking occurs at a link from nodes 18 to 20 if the demands 12, 22, and 30 are all assigned with the same wavelength.
Wavelength and/or subband blocking magnitudes depend on several factors. For example, blocking magnitudes depend on the number of intermediate nodes within the optical reach. The larger the number of intermediated switch sites within the optical reach, the more blocking needs to be resolved. However, this number is not something that can be limited unless an over-lay top tier network (with fewer switch sites) is created. Otherwise, the number of intermediate switch sites is totally dependent on the community-of-interest demands. Also, blocking magnitudes depend on the number of point to point demands in a network: The larger the number of different point to point demands, the more blocking occurs. Again, the number of point to point demands in a network cannot be limited unless an over-lay top tier network (with fewer switch sites) is created. Further, optical reach has an indirect effect on blocking magnitudes. Optical reach in itself does not have a direct effect on wavelength and/or subband blocking. However, in general, the longer the optical reach, the larger the number of intermediate switch sites within the optical reach, as above. The question arises—should optical reach be limited? The answer is no because the shorter optical reach would require more distance regenerators in a network. Still further, blocking magnitudes depend on system capacity. Generally, the larger the number of available wavelengths and/or subbands in a single system, the less the blocking. Again, the larger capacity of the systems would also help to reduce the number of systems needed to be deployed and thus reduce the overall cost.